We will develop a computer-microscope system designed to acquire and analyze quantitative morphological data obtained from many kinds of biological tissue. The system is an interactive one, that is, one which assists the biologist, by his command, during data acquisition and analysis. This minute-by-minute control permits the biologist to apply his own intellectual skills to image analysis while taking full advantage of the computational power, memory, control and graphical display functions of the computer. The system employs in a unique fashion the principle of image superimposition whereby, while looking through the microscope, the biologist can compare the original image of the tissue and its computer-analyzed version. At the same time he can also cause the system to execute such commands as: move the microscope stage, digitize the stage position, enter data into memory, generate graphic displays of these data. The system will be compact and easy to operate. Its software will be designed to permit easy modification to new tasks as they are defined and to changes in system hardware. The system promises to be of use in a wide variety of applications, the initial one being a neuroanatomical study of dendrites in the auditory cortex.